If you wanted to take high-speed Thalys (07:34, 08:34, 09:34 on weekdays - you don't say when this would be) as far as Antwerp (56 mins), booking up to 3 months in advance would save money - provided, of course, that nothing went wrong that stopped you from catching the departure in question, because Thalys tickets are only valid on the departure booked. But of course you can also buy tickets on the spot, and if this arrival is imminent, you would normally only be able to buy tickets at the top price anyway, so might as well do that.
There are non-high-speed IC departures (taking 1h38 to Antwerp) at 07:37, 08:37 and 09:37) for which the same applies in terms of reductions for advance purchase (which does not have to be so far in advance as with Thalys, I think it's something like minimum 1 week), but without the limitation to a specific departure; with an IC ticket, you can take any IC(/ICD) trains on the date in question.
You will see all options for your date and time on https://www.b-europe.com/EN entering Schiphol Airport as departure point and Brugge as destination. Brugge is a further 1h30 from Antwerpen-Centraal by IC trains only and for that part of your journey, again your ticket will cover any train from Antwerp to Brugge, going through (if not changing at) Gent St. Pieters. So if you select a specific Thalys departure and it gives a connection that involves a further change at Ghent (because there are at least twice as many trains from Antwerp to Ghent as to Brugge), there is nothing to stop you from waiting for the next direct departure from Antwerpen-Centraal to Brugge (6 mins past each hour, on weekdays) as you can use your ticket on that. Which would also give you time to see something of Centraal Station, which is worth looking at.Edited: 10 June 2018, 21:44